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Although she has access to earthquake monitors from across the world, Debi Kilb, a seismologist at the Scripps Institution of Oceanography, found out about Chile’s 8.8 magnitude earthquake on Saturday in the same way as most people — from the news.
Her next steps, however, were likely a little different.
“I flew out of bed, ran downstairs, turned on the computer, and made sure our computers at Scripps had recorded the earthquake,” she said. “Then I started pulling up other websites to see what the data looked like. I get a page on my cell phone every time there is an earthquake of 5.5 or above, so I scanned through my pages to see how big the aftershocks were.”
We sat down with Kilb to ask her about what she learns from these massive quakes, how the earthquakes in Haiti and Chile compare, and whether we can ever expect to see anything much bigger than an 8.8.
How did Chile’s earthquake compare to the one in Haiti scientifically?
An 8.8 magnitude has 1,000 times more energy released than a 7.0, which is what happened in Haiti. The reason for this is because Haiti sits on a smaller fault. The fault in Chile is very deep, and the magnitude of an earthquake correlates with the depth of the fault. That’s why the biggest earthquake ever recorded, a 9.5 in 1960, also happened in Chile.
It seems like there have been a lot of earthquakes this year. Is there an explanation for this?
There are actually about 15 magnitude 7.0 earthquakes every year. There is also usually about one each year of magnitude 8.0, but sometimes they are very deep so we don’t feel them as much. The reason Haiti was in the news so much was because of the death and destruction there, which was more because the building designs there are poor, not because of the earthquake.
How often does an earthquake as big as Chile’s happen?
About every 10 years there is an earthquake above an 8.0.
How did the Chilean earthquake’s strength rate against what’s possible?
There was the 9.5 in 1960, but I don’t expect it could get too much larger than that. It’s not realistically possible to go above a 10.
Can you explain physically what exactly happened in the Chilean earthquake?
There are tectonic plates under Earth’s surface that are constantly moving, but very slowly. Their max speed is probably as fast as our hair grows. In this earthquake, it was one plate sliding under the other, creating a collision. This kind of collision is where we expect the biggest earthquakes.
What do big earthquakes like these teach you as a seismologist?
It shows us how far away aftershocks are going to be. In the last few decades we’ve completely changed what we think about this. Now we know that earthquakes’ aftershocks can be very far away. From this earthquake, it looks like there was triggering in Yellowstone and some in Owens Valley. We also saw some anomalous earthquakes here in Rose Canyon, but we don’t know yet if we have enough information to say they’re related.
We can also find if they’re triggering at volcanoes, and see how much stress or strain changes we see there. And we can also look at if there are tremors along other faults. It is basically a madhouse with the amount of data we can look at.
In your own research, you mainly study aftershocks. Why is that?
There are so many more aftershocks, so there is tons more data. I’m asking if small earthquakes are the same as big earthquakes, meaning if we scale up the magnitude of a small earthquake, will it look the same as a big one? If we better understand what triggers aftershocks, we can then better understand what triggers main shocks.
Do you think we’ll ever be able to predict when an earthquake is coming?
Well, right now we can say that in the next 100 years there will be an earthquake on the San Andreas Fault, but the idea is to be a little more precise than that. I used to think that in my lifetime we wouldn’t be able to predict, but there is so much data coming in now that I think it could be possible. There’s probably something in the data we haven’t found yet that will signal something to us.
Do you need these big earthquakes to happen for your research?
It definitely helps, because it allows us to lower the uncertainties in our data. If you only look outside the window in San Diego on one day and it happens to be torrential downpours that day, you might think that’s always what the weather will be. But if we repeat that measurement four, five, or six times, we can see better what the uncertainties are. We need more data points.
— CLAIRE TRAGESER